The present invention relates to the field of electromagnetic pumps, and further relates to the use of low power electromagnetic pumps for use in implantable medical device applications.
Presently, small pumps are used to pump liquids such as medicines, drugs, insulin, chemotherapy liquids, and other life critical drugs to a patient. These pumps are sometimes required to be quite small given the fact that they oftentimes will be implanted into the patient""s body. If they are implanted, it is desirable that the pump have a low power requirement so that the battery which powers the electromagnetic pump has a long life. A battery with a long working life is therefore desirable for use in such instances.
In the past, the low power electromagnetic pumps available in and used for the purposes described above were complex mechanisms. Complex not only in the manner in which they functioned, but also complex in the manner in which they were made. Indeed, a drawback associated with the prior pumps is that they are made of a plurality of complex parts. These parts are difficult to manufacture due to the size requirements of the pump. Take for example the armature of a typical prior pump. In the past, the armature was made of a plurality of complex delicate parts, all of which had to be arranged inside the pump housing in an equally delicate and complicated process. Positioning and aligning these parts in the pump housing was a difficult and tedious task. Also, these pumps required excessive amounts of time to manufacture the intricate components, meaning mass production of the components was simply not a viable option.
A requirement of such a pump is that it have a low power drain, since the pump will in many applications be powered by an implanted battery. Another requirement is that the pump be compatible with the drugs/fluids being pumped. Other requirements are that the pump have a simplified structure and method of assembly while simultaneously having improved performance. More requirements are that the pump operates in a manner preventing damage to fragile drugs, such as insulin, and that moving parts of the pump be resistant to wear, thus prolonging the pump""s useful working life.
It would therefore be desirable to provide an electromagnetically operated pump which is safe, reliable, small in size, light in weight, operates with low power requirements, and which is compatible with drugs, such as insulin, or other liquids to be pumped, and which has a relatively simple structure and method of assembly and improved performance. It would also be desirable to provide a pump having parts able to be mass produced efficiently and without difficulty, and it would be useful if the actual assembly of the pump was simplified such that assembly time is reduced. This would result in an reliable pump that can be mass produced at lower production costs, a pump that operates in a manner preventing damage to fragile drugs such as insulin, and a pump that is resistant to the detrimental effects of the drugs, insulin, or other fluids being pumped, and which has wear resistant moving parts.
The low power electromagnetic pump operates at an extremely low power, and it may be used in implantable drug delivery systems, although the principles of this invention can be variously applied. That is, the low power electromagnetic pump also may be employed in applications external to a patient""s body.
The present invention provides an electromagnetic pump comprising a housing having an interior fluid containing region including a fluid receiving chamber in communication with an inlet, a fluid output chamber in fluid communication with an outlet, and a check valve means operatively associated with the fluid containing region for allowing fluid flow in a direction from the inlet toward the outlet and blocking fluid flow in a direction from the outlet to the inlet. Electromagnet means are carried by the housing and located external to the fluid containing region, and barrier means of fluid impervious material isolates the electromagnet means from the fluid chambers. An armature is positioned in the housing and comprises a pole portion located for magnetic attraction by the electromagnet means and has a plunger portion joined with and extending from the pole portion. The armature is supported in the housing for movement from a rest position through a forward pumping stroke when attracted by the energized electromagnet means to force fluid from the output chamber through the outlet, and for movement in an opposite direction through a return stroke back to the rest position when the electromagnet is de-energized.
The armature comprises a pole face portion and a plunger portion, with the plunger portion comprising and a first shaft portion, a second shaft portion of greater diameter than the first shaft portion, a third shaft portion of greater diameter than the second shaft portion, and a head portion of greater diameter than the third shaft portion. The armature plunger portion can be machined from a piece of plunger stock, thus providing for a one piece plunger portion. The plunger portion may comprise, for example titanium, titanium alloys, metals, and biocompatible materials. An inner weld ring joins the head portion with the pole portion. The pole portion is encased in a in a titanium shell and holds a body of magnetic material. A retainer element is joined to the second shaft portion, and the main spring is captured between the retainer element and a retainer plate. The main spring is for storing energy during a forward pumping stroke and releasing energy during the return stroke. Guiding of the armature as it reciprocates is provided by the cooperation between the outer surface of the first plunger section and the adjacent housing of the pump.